1. Field of the Invention
The present invention relates to computer networks and more particularly to computer networks in which mobile computers are wirelessly connected to the network.
2. State of the Art
In recent years, a powerful computing trend has been toward giving groups of computer users access to the power of shared resources, all linked together on a network, for example a local area network (LAN). Today, LANs are common in offices, enabling users of personal computers to share files and other resources. In a network, a "server" is a network resource that makes files and applications--and hardware, i.e. printers--available to network users. An "access point" is a node directly accessible to a server. A "router" is a device that enables several sub-networks to be linked together to form an encompassing internetwork. Routers are store-and-forward devices and are able to route packets around failed routers or congested sections of the network. Access points are provided using routers. A server may also function as a router.
Traditionally, networks have been linked together by wire cables. More recently, wireless LANs have been made available in which wire cables are replaced by radio links, enabling mobile computers to be networked together. A user equipped with such a mobile computer may move from place to place free of cabling constraints. By providing mobility within the computer network the utility of the network is greatly increased.
Computing devices connected together in a network run under a network operating system. A popular network operating system is NetWare.RTM. sold by Novell, Inc. NetWare is a mature network operating system, developed largely before the commercial development of wireless LANs. Therefore NetWare, despite being a very full-featured network operating system, does not readily support networked mobile computing. A desirable capability in a network mobile computing environment is that mobile computers be able to freely roam throughout the entire internetwork without interruption of communications and without the necessity of user intervention (i.e., "seamless" roaming).
NetWare presently does not allow roaming of the type described. Rather, NetWare, at the current time, requires that the network ID of a network entity (or node) remain constant for the duration of a session. NetWare uses the combination of the network number and physical address of a node as a network ID. If a network node were to attempt to switch access points by attaching to different router or server during a session, NetWare would require that the network number of the new connection be identical to that of the previous connection. If two NetWare subnets use the same network number, they must be connected on the same "cable" (or networking medium), else router errors will be generated. In a networked mobile computing environment, access points may not be able to communicate with each other, since they may be out of range of each other or on different radio channels or sub-channels. Therefore, the use of the same network number for all access points is not feasible.
What is needed, then, is a mechanism for providing roaming capability to mobile computers within a standard network such as a Novell network.